Cathode structure



Nov. 26, 1946.-

P. G. CHEVIGNY CATHODE STRUCTURE Filed Feb. 6, 1943 INVENTOR. Pfll/L c1. CHEV/GNY AT ORLZEY Patented Nov. 26, 1946 UNITED STATES PATENT OFFICE I 2,411,50 7 y i CATHODE STRUOTUBE" v I Paul Georges Chevigny, New York, N. -'Y. assignor to Federal Telephone and Radio- Corporation, Newark, N."J., a corporation of Delaware Application February 6, 1943, Serial No. 474,953

cciaims. (01. 1250-275) 1 This invention relates to improveinentsin cathode structures and methods'of assembling the same, and more particularly to indirectly heated cathodes for vacuum tubes. v An object of this. inventionis'to provide an "improved, easily assembled cathode structure.

Another object of this invention is to provide anim'proved novel cathode assembly.

7 l A furtherobje'ct of this invention is the provision of an improved indirectly heated cathode comprising an easily assembled, closely spaced spiral or a plurality of interwound spirals, presenting a continuous emitting surface having a relatively large emitting area.

Other objects and advantages of the present invention will become apparent from the following detailed description of a preferred embodiment of the invention, together with a modification thereof, illustrated in the accompanying drawing in which:

Fig. 1 is a longitudinal sectional view of a cathode assembly formed in accordance with the present invention;

Fig. 2 is a bottom view of trated in Fig. 1; and

Fig. 3 is a plan view of a composite interwound cathode, which may be used in connection with 1 the assembly illustrated in Fig. 1.

In the preferred form of invention shown in Figs. 1 and 2, the cathode l consists of a single spiral of pre-set carburized tungsten wire, the turns of which are closely spaced so that they will form a substantially continuous outer emitting surface. The cathode III is slipped over a plurality of supporting rods l6 formed, for example, of tungsten. These rods arecircumferentially spaced in such a manner that their common outer circumference issubstantially equal to the inner periphery of the spiral cathode; as a result the cathode will fit snugly about the rods and the rods will prevent relative lateral movement of the cathode spiral.

The cathode I0 is held on the rod it against longitudinal movement between a pair of end rings l8 and which may be, for example, tanthe assembly illustalum wires welded to and about the rods 16.

The rods 16, illustrated aS four in number are preferably mounted in a supporting member 22, as more clearly shown in Fig. '2, this supporting member being held in place, in turn, by a rod 24 serving as a cathode lead and projecting through the seal of the vacuum tube (not shown).

The member 22 may be formed with a radial slot 26 through which pass a pair of heater filament leads 28 and 30. The centrally positioned lead 28 extends downwardly substantially to the bottom of the cathode l0, andat this point is 1 connectedto one end of a concentric spiralfilament 32. {The upper end 34 of the filament-32 is co'nnectedgto thesecond lead 30. The; leads 28 andare also adapted to pass through and be, supported by thevacuum tube seal. .fIn'place or a single closely wound spiral cathode 10, there may be provided a cathode in the form of two or morewidely spaced spirals screwed :one intothe other, the spacing; between spirals being such that they will form a continuous emit- "tin'g surface .when'fully, interwound. ar-

rangement illustratingtwo such spirals forming a composite cathode is illustrated in Fig. 3. This figure shows the spiral 50 partially screwed into the spiral 52. In use, the two spirals would be screwed together so that total length of the oathode would be the same as that of a single spiral cathode such as illustrated in Fig. 1; they have been illustrated as partially unscrewed in Fig. 3 solely for the sake of clarity.

The advantages of the foregoing invention will, it is believed, be clear to those skilled in this art. A cathode of the form disclosed in which the turns are so closely spaced as to be touching one another will form a, continuous emitting surface which will have a greater emitting area than a comparable cathode wound, for example, from 30 flat hands. This is due to the fact that the emitting surface is increased by half of the circumference of each turn relatively to its diameter or in the ratio of This will result in appreciable gain although not entirely proportional to the increased area, since the electrons emitted between the wires are more difiicult to draw out. The fact that in all cases the turns of the spiral are touching to form a substantially closed cylinder permits the advantageous use of this type of cathode with a filament which is adapted to heat the cathode by bombardment. One of the outstanding advantages of the present structure lies in its ease of assembly. It is only necessary to attach one end ring such as the ring I8 about the supporting rods l6, slide the cathode over the rods against this ring, and then add the ring 20 at the other end of the cathode, squeezing the cathode against the ring l8, and attaching the ring 20 to the supporting rods.

Other advantages of the present structure to- 55 gether with obvious modifications thereof, all

coming within the scope of the present invention as set forth in the objects and claims, will be apparent to those skilled in this art.

I claim:

1. A cathode for electron discharge devices comprising, in combination, a supporting member, a plurality of circumferentially positioned rods mounted in-saidi s lpportin :member, .a rin extending about and attachedto all of said rods, a closely spaced helical winding of substantially uniform diameter extending about said rods and supported by said ring and unattached :tothe rods, and a second ring extending about and attached to all of said rods at the other end of said winding for holding the same in place 'on said rods between the two rings.

2. The combination according to claim 1, in which said winding consists of a single closely spaced spiral of wire forming a continuous outer surface.

3. The combination according to claim 1, in which the-common outer circumference of the circumferentially positioned rods is substantially equal to the inner periphery of the rings and of the winding, whereby therods hold thewinding against lateral movements and the rings hold the windin against longitudinal movement.

4. A cathode "for electron :discharge devices comprising, in combination, a supporting -member, a pluralityof circumferentially positioned rods mounted in saidsupporting member, a ring extending-aboutandattached'to all of said rods, a closelyzspaced helical windingof substantially uniform diameter extending about said rod and supported by said ring, said winding consisting of a plurality of interwound closely spaced spirals forming a continuous outer surface, and a second ring extending about and attached to all of said rods at the other end of said winding for holding the same in place on said rods between thetwo rings.

"5. An electrode for electron discharge devices comprising, in combination, a supporting member, a plurality of circumferentially positioned rods mounted in said supporting member, a cylindrical member of substantially uniform diameter extending about said rods and capable of longitudinal movement in relation to said rods,

-rods adjacent and abutting opposite ends of said winding.

PAUL GEORGES CHEVIGNY. 

